1. Field of the Invention
The invention relates to a worm gear transmission comprising a worm wheel journalled in a housing and a worm which engages the wheel; and in particular to a transmission having a worm arranged between two bearings, the first bearing being pivotably connected to the housing and the second bearing being engaged by an adjustable pre-loading spring which exerts a force on this bearing pressing the worm toward the worm wheel.
2. Description of the Prior Art
An anti-backlash worm gear transmission of this kind is known from Bauelemente der Feinmechanik, Richter und Vos (1952), pp. 417-418. The play in this known transmission is eliminated by pivotally mounting the worm bearing in the housing on one end, and by loading the worm to a predetermined value at the other end, by a spring, so that the worm is pressed into the worm wheel. The value of the pre-loading force exerted by the spring must be such that the maximum force occurring on the worm during operation, opposing the spring force, is exceeded; as a result both flanks of the engaging teeth remain in contact with each other.
This means that in all circumstances the total tooth load exceeds, by an amount equal to the maximum operating load for which the pre-loading is sufficient, the value which is caused by the instantaneous operating load. Consequently, when operating load is at its anticipated maximum, the total load equals twice this maximum value; while at zero operating load the total load equals the maximum operating load.
This design has the drawback that far more wear occurs and much more frictional heat is developed than if no pre-loading force were used.